Formation, Survival, and Detectability of Planets Beyond 100 AU
Direct imaging searches have begun to detect planetary and brown
dwarf companions and to place constraints on the presence of giant planets
at large separations from their host star. I help motivate such planet
searches by predicting a population of young giant planets that could be
detectable by direct imaging campaigns. Both the classical core accretion and
the gravitational instability model for planet formation are hard-pressed to
form long-period planets in situ. I will show that dynamical instabilities
among planetary systems that originally formed multiple giant planets much
closer to the host star could produce a population of giant planets at large
(~100 AU - 100000 AU) separations. I estimate the limits within which these
planets may survive, quantify the efficiency of gravitational scattering into
both stable and unstable wide orbits, and demonstrate that population analyses
must take into account the age of the system. I predict that planet scattering
creates a population of detectable giant planets on wide orbits that decreases
in number on timescales of ~10 Myr. I demonstrate that several members of such
populations should be detectable with current technology, quantify the
prospects for future instruments, and suggest how they could place interesting
constraints on planet formation models. I will open with a brief review of the
state of the field and an exoplanet database comparison.